The invention relates to a liquid crystalline material in the form of an anisotropic gel comprising a polymerized liquid crystalline material and a low-molecular weight liquid crystalline material. The invention further relates to a display cell comprising two facing plates which are transparent to light, which plates are provided on the sides facing each other with an electrode of a material which is also transparent to light, each electrode carrying a transparent orientation layer, a sealing material which is in the form of, for example, a ring, between the plates and, a liquid-crystalline material in the space between the plates and the sealing material.
In WO89/09807, a material is disclosed which consists of microdrops of a liquid crystalline material dispersed in a polymeric matrix of a liquid crystalline material having mesogenic groups. In said publication it is stated that the matrix material is of the thermoplastic type, indicating linear polymers. Said linear polymers can be used in electro-optical light shutters because, dependent upon the structure of the microdrops and the configuration of light shutter, said light shutters are bistable for example, translucent in the OFF-state and opaque in the ON state.
In WO89/06371, a composite material is disclosed which consists of drops of liquid crystalline material within a matrix of a polymer of acrylic acid, said liquid crystalline material having a solubility in the polymer which is lower than its solubility in the corresponding monomer. After polymerization of the monomer, this composite material is a solid matrix in which the liquid crystalline material is dispersed in the form of drops. In this manner, problems concerning the leaking of the liquid material from the display cells are overcome. In U.S. Pat. No. 4,891,152, a similar material is disclosed, with the difference that a matrix is formed from a copolymer of an acrylate and a mercaptan.
In European Patent Application EP 291427, a description is given of a polymer of a liquid crystalline material having mesogenic groups in the side chain and an ethene-like unsaturation. These linear polymers may be mixed with variable quantities of small molecules which have no side chains, which small molecules may be mesogenic. The orientation of the linear polymers can be changed when the external field is changed, whereas the orientation of a network remains unchanged.
European Patent Application EP 313053 describes the use of a liquid crystalline material having a positive dielectric anisotropy with a transparent solid, which is present in the liquid crystalline material in the form of particles on a three-dimensional network. The network, however, is not composed of a liquid crystalline material and it is not oriented.
As described in an article by Rudolf Zentel, published in 1986, vol. 1, No. 6, pages 589-592, cross-link crystalline polymers are made to swell by using low-molecular weight nematic liquid crystal materials, so that orientation in electric fields can be brought about more readily. Two polymer materials having a different cross-linking density are used, such as 1) polyacrylate having side groups to obtain a liquid crystalline material and 2) polymethacrylate.